1. Field
Aspects of the present invention relate to a process, voltage, and temperature (PVT) tolerant differential circuit and a comparator including the PVT tolerant differential circuit.
2. Description of Related Art
A differential circuit (or differential amplifier) is a kind of electronic circuit that amplifies the difference between two input signals. A common configuration of a differential circuit is a differential pair, which includes two amplifying stages with common degeneration.
Many electronic devices use differential circuits. For example, a comparator, which is a device that compares two input signals and outputs a signal based on this comparison, may use a differential circuit. In one configuration, a comparator receives two input signals and outputs a signal indicating which of the received signals is larger. In another configuration, a comparator receives two signals (e.g., two complementary signals) and outputs a signal indicating whether or not the difference between the two received signals is greater than a detection level.
A comparator implemented to perform the above-described level detection has numerous applications, including multilevel serial/parallel links, analog-to-digital converters, and peak detection. Mismatched differential circuits (e.g., circuits with mismatched amplifier stages) may be used in a comparator to set the offset voltage adjustment and for level detection. Enabling a wide range of detection levels is desirable to extend the usable range of a comparator circuit (e.g., to increase the detection range).
Additionally, it is desirable to have differential circuits which are resilient to environmental or process variations. For example, in multilevel systems, the various detection level voltages should, ideally, remain constant under process, voltage, and temperature (PVT) variations; otherwise the system may fail, may be error prone, or may require over-designing to accommodate the variations. As described above, the detection level voltages may be set using mismatched differential circuits; however, the detection levels of mismatched differential circuits are a function of the overdrive of the mismatched differential circuits, which may vary across PVT conditions.